This section introduces information that may be related to or provide context for some aspects of the techniques described herein and/or claimed below. This information is background facilitating a better understanding of that which is disclosed herein. Such background may include a discussion of “related” art. That such art is related in no way implies that it is also “prior” art. The related art may or may not be prior art. The discussion is to be read in this light, and not as admissions of prior art.
Pipes formed from polyethylene, and polyolefins such as polyethylene have been used in commercial plastics based on their outstanding performance and cost characteristics. High density polyethylene has been used in commercial applications such as pipe production due to its chemical and physical resilience, e.g., its impact resistance and its ability to withstand thermal extremes. The production and value of high density polyethylene pipe may be dependent on factors which include the extrudability of the polymeric resin and the resistance of the resulting pipe to sagging, which may occur during melt extrusion of thick-walled pipe, and which leads to unacceptable pipe wall thickness variation around the pipe circumference.